1. Field of the Invention
This invention relates to a carburetor for vehicle and particularly to a changeable venturi carburetor with cold start and high loading auxiliary fuel duct that can automatically supply additional fuel gas into the engine to provide extra power when needed.
2. Description of the Prior Art
The function and purpose of carburetors in (automobile or motorcycle) is to provide appropriate fuel gas mixture for engine to generate power needed at different work load conditions. Conventional carburetor includes a Venturi tube. When air flows through the Venturi throat, airflow speed increases and results in vacuum effect. Fuel nozzle sucks in fuel. Fuel is then vaporized to mix up with air for engine combustion use.
When a vehicle is under cold start situation, it needs rich fuel gas mixture to start the engine. Conventional vehicles use the throttling method and means to meet this need. It is not very satisfactory, particularly in winter time when temperature is low. It often happens that the vehicle is difficult to start, or the engine does not run smoothly and will take a long time to warm up. It is time consuming, causes fuel waste and creates air pollution as combustion in the engine usually is not completed during cold start and warm up period.
Another situation is when the vehicle is in motion but needs sudden high power such as abrupt acceleration or climbing a high slope road. Hitting the accelerator heavily and suddenly trying to get extra power needed will result in a vacuum drop in the engine and creating a situation wherein cannot provide adequate fuel gas mixture for engine combustion. Engine output will drop. Total engine displacement will be impacted and results in poor engine performance. These shortcomings indicated that improvements are needed.